PURPOSE: To obtain the subject compd. at a good yield with high purity from an easily available nitrile and alcohol via an iminoester hydrohalide, a hydroxamic acid ester and an oxime ether, and finally by hydrolysis.

CONSTITUTION: The O-substituted hydroxylamine of formula IV is obtd. by bringing a nitrile of the formula R6-CN (R6 is an alkyl, phenyl, benzyl) and an alcohol of the formula R7-OH (R7 is an alkyl, benzyl, an alkoxyethyl) into mutual reaction under the presence of a hydrogen halide in an org. solvent slightly miscible or entirely immiscible with water to obtain an iminoester hydrocarbon halogenide of formula I (X is Cl, Br, I), adding the compd. to an aq. suspension of carbonate or hydrogencarbonate, further adding an aq. soln. of a hydroxylamine salt thereto, separating and removing the water phase to obtain an hydroamic acid ester of formula II, then subjecting the compd. to O-alkylation with an alkylating agent of the formula Y-R1 (R1 is an alkyl, a haloalkyl, etc.) to obtain an oxime ether and finally subjecting the compd. to hydrolysis thereby obtaining the O-substituted hydroxylamine of formula IV. The required time is short and the process is simplified.